Facebook Inc has been working to expand its presence on people's mobile devices by creating and buying apps such as Messenger, Paper, Instagram and WhatsApp.
The apps Facebook created from scratch through its Creative Labs have faced varying levels of success.
Paper, a mobile news reader, hasn't really caught on.
Slingshot was launched as a rival to the ephemeral messaging service Snapchat but it hasn't been much of one. Facebook declined to provide user figures for Creative Labs apps.
Messenger, which is not from the company's Creative Labs division, has fared much better, though it helped that Facebook essentially forced users to download it after it removed the messaging functionality from its main app.
Unlike with Messenger, though, the company says it won't require people to use the stand-alone app if they want to use Facebook Groups. They will be able to access Groups through the Facebook app or for free on the website.
More than 700 million of Facebook's 1.35 billion members use Groups, according to the company. People use the groups to talk to others who share their religion, to plan holiday dinners, or to discuss hobbies or heath issues, for example.
Shirley Sun, product manager at Facebook, said there are "hundreds of millions" of groups on Facebook.
The new app lets people manage their existing groups or discover new ones, either based on recommendations or by searching for different topics.
Users can also create a shortcut on their phone's screen for their favorite group if they want to access it quickly.